Topical composition for pain relief

ABSTRACT

Described is a topically applied composition relief of pain. Also described are methods of preparing the composition and methods of using the composition to relieve pain.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions and methods for pain relief.

2. Description of the Related Art

Pain results from the noxious stimulation of nerve endings. Nociceptive pain is caused by stimulation of nociceptors (e.g., a needle stick or skin pinch), which then transmit impulses over neural pathways to the spinal neurons and then to the brain. Neuropathic pain is caused by damage to neural structures, such as peripheral nerve endings or nociceptors, which can generate impulses in the absence of stimulation (e.g., herpes zoster pain after the rash has healed).

In contrast to pain treatment with systemic agents, pain can be treated locally by topically administering a pain relieving agent directly to the painful area to block the nociceptive mechanistic pathway. Local anesthetics prevent the generation and conduction of nociceptive nerve impulses. Thus, for example, a local anesthetic or analgesic can be topically applied at the pain area. Advantages of topical anesthetic or analgesic administration over systemic administration of pain relievers include decrease or preclusion of certain side effects, improved patient compliance, and reversible action (i.e., the action can be reversed by removing the anesthetic from the application site).

A variety of drug classes have anesthetic or analgesic properties and can be administered in topical formulations. Traditional local anesthetics or sodium-channel blockers, such as lidocaine prevent the generation and conduction of nerve impulses by decreasing or preventing the large transient increase in the permeability of excitable membranes to Na+. Other agents with analgesic properties include the non-steroidal anti-inflammatories (“NSAIDs”) and opioids, such as morphine.

It is common practice to provide a topical pain reliever using the well-known NSAID, salicylic acid (aspirin). Aspirin has been used effectively for many years in the medical and scientific community as a pain reliever. Despite its benefits, systemic administration of aspirin has been shown to cause certain side effects in its users, for example stomach irritation and other internal problems associated with ingesting aspirin.

Applying an aspirin solution topically to a user's skin, thereby avoiding the need for a user to ingest aspirin, has been shown to be an effective manner of gaining the benefits of aspirin without the potential side effects. However, there are difficulties associated with the ability to achieve a safe and stable form of a topical pain reliever containing aspirin that will remain in suspension within the solution of the topical pain reliever.

In view of these difficulties, other NSAIDs have been utilized for their anti-inflammatory or analgesic properties. It is an important aspect of any NSAID-based topical pain reliever to permeate the necessary layers of the integument or skin in order to relieve pain without adversely affecting vital internal organs. Accordingly, it is accepted that an effective topical pain reliever should be in the form that dissolves the analgesic agents and transports it to the area of pain where it can then permeate the integument or skin to provide effective relief.

Topical pain relievers have been introduced in the past, but such topical pain relievers have traditionally had problems of maintaining the analgesic in suspension within the solution of the topical pain reliever. Further, topical pain relievers have been known to have a delayed onset of action after they have been applied to the integument or skin. Several reasons may cause such a result, for example the topical pain reliever may not effectively permeate the skin.

Many patients with localized pain due to arthritis, bursitis, sprain or muscle strain, bruises or hematomas cannot tolerate conventional NSAIDS. In addition, topical administration of conventional NSAIDS has been known to be ineffective because only a therapeutically ineffective amount of the drug can penetrate the skin. In addition, indications such as acne, psoriasis and eczema are typically refractory to topical or oral administration of NSAIDS.

In addition, joint pain can often indicate the onset of a condition called osteoarthritis. Osteoarthritis is a degenerative joint disease affecting articular cartilage developing in the fourth and fifth decades of life that was initially believed to be a disease of wear and tear due to mechanical stress on the joints. It is now known that the pathology of osteoarthritis is not entirely mechanical and involves changes in the joint metabolism. Specifically, altered glucosamine metabolism appears to play a key role in the development of osteoarthritis.

An effective treatment of osteoarthritis must address two types of problems: (i) pain, and joint tenderness, swelling and stiffness must be alleviated as an immediate patient's problem; and (ii) the degenerative process must be stopped preferably at its earlier stages. Treatment with anti-rheumatics and NSAIDs has not proven successful. Anti-rheumatics, although quickly effective, were recently shown to impair the very function that physicians were trying to improve, and anti-inflammatory drugs alleviate the pain but do not address the underlying degenerative disorder.

Therefore, what is needed is a topical composition that provides effective pain relief, is stable for long periods of time and provides a long shelf-life, and avoids the disadvantages associated with other topical analgesics or systemically administered drugs. What is further needed is a composition that is effective in treating a wide variety of inflammatory conditions by topical application of the composition.

These advantageous properties are provided by the composition set forth in the description that follows. Further advantages will be apparent from the description, or may be realized by the practice of the invention without undue experimentation.

SUMMARY OF THE INVENTION

The subject invention concerns a composition which can be topically applied to the skin for the relief of pain at the site of application. An embodiment of a composition according to the invention comprises an effective amount of at least one anti-spasmodic or GABA-agonist, at least one local anesthetic agent, at least one α₂-adrenergic agonist, at least one NMDA-receptor antagonist, at least one Non-Steroidal Anti-inflammatory Drug (NSAID), at least one serotonin-norepinephrine reuptake inhibitor (SNRI), together with a solvent in a cream or ointment base.

A preferred embodiment for the composition of the subject invention comprises, in a cream or ointment base (inactive pharmaceutical compounding base):

-   -   about 1-20% anti-spasmodic or GABA-agonist     -   about 1-5% local anesthetic agent     -   about 0.1-1.0% α₂-adrenergic agonist     -   about 1-20% NMDA-receptor antagonist     -   about 1-20% Non-Steroidal Anti-inflammatory Drug (NSAID)     -   about 1-10% Serotonin-Norepinephrine Reuptake Inhibitor (SNRI),         and     -   about 1-10% solvent.

The cream or ointment pharmaceutical compounding base can comprise about 25% to about 75% (w/w) of the composition, and preferably comprises about 50% to about 60% of the composition.

In a more preferred embodiment, the subject composition comprises, in a cream or ointment base:

-   -   gabapentin—1-10% (anti-spasmodic or GABA-agonist     -   baclofen—1-10% (anti-spasmodic or GABA-agonist)     -   lidocaine HCl—1-10% (local anesthetic agent)     -   clonidine HCl—0.1-1.0% (α₂-adrenergic agonist)     -   ketamine HCl—1-20% (NMDA-receptor antagonist)     -   ketoprofen—1-20% (NSAID)     -   amitriptyline HCl—1-10% (SNRI)     -   DMSO—1-10% (solvent)

The above ingredients are preferably mixed with or into a pharmaceutical compounding base, such as PENcream, which makes up the balance of the composition, and typically comprises about 50-60% of the composition.

In a most preferred embodiment, a composition of the subject invention comprises:

-   -   gabapentin—5%     -   baclofen—4%     -   lidocaine—5%     -   clonidine—0.2%     -   ketamine—10%     -   ketoprofen—10%     -   amitriptyline—2%     -   DMSO—5%     -   PENcream base—58.8%

The subject invention further comprises a method of preparing the disclosed embodiments of the composition. For example, the process comprises the following steps:

-   -   1. adding all active pharmaceutical ingredients (APIs) in a         single vessel;     -   2. adding to the APIs about 75% of the final amount of         compounding base;     -   3. adding the solvent (e.g., DMSO) to the APIs in 75%         compounding base;     -   4. mixing the APIs in 75% compounding base and solvent for about         2 minutes using a mixer at relatively high speed (e.g., level 9         of 10);     -   5. adding the remaining about 25% of the compounding base to         form a final mixture;     -   6. mixing the final mixture using a mixer until the mixture is         substantially homogenous, typically for about 7 minutes at high         speed (level 9 of 10).

The subject invention further comprises a method of using the composition, for example, topically applying a safe and effective amount of the composition to the skin for the treatment of pain caused by joint stiffness, arthritis, swelling, Inflammation or edema, muscle cramps or tremors, or for relief of discomfort from sensations such as a “burning” sensation or pain, or unspecified tingling sensations in limbs or hands or feet. An effective amount is typically an amount to cover the area experiencing the pain or sensation.

It is therefore an object of the present invention to provide a composition and method for the topical or transdermal relief of pain to provide immediate, long-lasting and cumulative relief from pain and inflammation of sore or stressed muscles and joints.

It is yet another object of the present invention to provide a pain relief composition comprising a plurality of Active Pharmaceutical Ingredients, which is effective and comfortable to apply to the skin.

It is yet another object of the present invention to provide a soothing, anti-inflammatory complex for the joints and muscles, which can be used in combination with other pain relief agents.

Other objects and advantages of the present invention will be apparent from a review of the following specification.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description of exemplary embodiments and is not intended to represent the only forms in which the exemplary embodiments may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for preparation and/or use of the exemplary embodiments. However, it is to be understood that the same or equivalent functions and sequences which may be accomplished by different exemplary methods are also intended to be encompassed within the spirit and scope of the invention.

As used herein, “safe and effective amount” means a sufficient amount of a compound, composition or other material described by this phrase to significantly induce a positive modification in the condition being treated, but low enough to avoid undue side effects (e.g., significant skin irritation or sensitization), within the scope of sound judgment of the skilled person. The safe and effective amount of the compound, composition or other material may vary with the particular person being treated, factoring the age and physical condition of the biological subject being treated, the severity of the condition, the duration of treatment, the nature of concurrent therapy, the specific compound, composition, or other material employed, the particular carrier utilized, and the factors within the knowledge and expertise of the skilled person.

A composition according to the subject invention comprises the following active pharmaceutical ingredients (APIs):

-   -   1. At least one anti-spasmodic or GABA-agonist. A preferred         embodiment of the subject composition comprises two         anti-spasmodic or GABA-agonist APIs, most preferably gabapentin         and baclofen. Gabapentin powder and baclofen, USP, are available         commercially from Medisca (Plattsburg, N.Y.). Examples of other         anti-spasmodics or GABA-agonists that can be used in a         composition of the subject invention include, but are not         limited to: Acamprosate, Picamilon, GHB, benzodiazepines,         nonbenzodiazepines (e.g., Zolpidem, Zopiclone, Zaleplon),         barbiturates, methaqualone, muscimol, progabide, and tiagabine,         or salts, derivatives, isomers, polymorphs, or esters thereof.     -   2. At least one local anesthetic agent. A preferred embodiment         of the subject composition comprises lidocaine, more preferably         lidocaine HCl monohydrate, in the form of a solid powder as a         local anesthetic component of the subject composition. Lidocaine         HCl monohydrate is commercially available from Medisca         (Plattsburg, N.Y.). Examples of other local anesthetics that can         be used in a composition of the subject invention include, but         are not limited to: local anesthetic esters, selected from the         group Procaine, Benzocaine, Chloroprocaine, Cocaine,         Cyclomethycaine, Dimethocaine/Larocaine, Piperocaine,         Propoxycaine, Procaine/Novocaine, Proparacaine. and         Tetracaine/Amethocaine; local anesthetic Amides, selected from         the group Articaine, Bupivacaine, Cinchocaine/Dibucaine,         Etidocaine, Levobupivacaine, Lidocaine/Lignocaine, Mepivacaine,         Prilocaine, Ropivacaine, Trimecaine; salts, derivatives,         isomers, polymorphs, or esters thereof, or combinations thereof.     -   3. At least one α₂-adrenergic agonist. A preferred embodiment of         the subject composition comprises clonidine, preferably         clonidine HCl as an α₂-adrenergic agonist component of the         subject composition. Clonidine HCl, USP, is commercially         available from Medisca (Plattsburg, N.Y.). Examples of other         α₂-adrenergic agonists that can be used in accordance with the         subject composition include, but are not limited to: Guanfacine,         Guanabenz, Guanoxabenz (a metabolite of guanabenz),         Guanethidine, Xylazine, Tizanidine, Methyldopa, and Fadolmidine,         or the salts, derivatives, isomers, polymorphs, or esters         thereof. Other agents that classified as α-adrenergic agonists         but which have not been determined as α₁- or α₂-adrenergic         agonists include: amidephrine, amitraz, anisodamine,         apraclonidine, brimonidine, cirazoline, detomidine,         dexmedetomidine, epinephrine, ergotamine, etilefrine,         indanidine, lofexidine, medetomidine, mephentermine,         metaraminol, methoxamine, mivazerol, naphazoline,         norepinephrine, norfenefrine, octopamine, oxymetazoline,         phenylpropanolamine, rilmenidine, romifidine, synephrine,         talipexole, and tizanidine, or salts, derivatives, isomers,         polymorphs, or esters thereof. To the extent these agents are         identified as α₂-adrenergic agonists, they may be substituted         for clonidine HCl in a composition of the subject invention.     -   4. At least one NMDA-receptor antagonist. A preferred embodiment         of the subject composition comprises ketamine, preferably         ketamine HCl as an NMDA-receptor antagonist component of the         subject composition. Ketamine HCl, USP, is commercially         available from Medisca (Plattsburg, N.Y.). Examples of other         NMDA-receptor antagonists that can be used in accordance with         the subject composition include, but are not limited to:         Amantadine, Phencyclidine (PCP), Dextromethorphan or         dextrorphan, Memantine, Riluzole, HU-211 (also a cannabinoid),         Conantokins, or the dual opioids and NMDA-Antagonists:         Ketobemidone, Methadone, Dextropropoxyphene, Tramadol, Kratom         alkaloids, or Ibogaine. These compounds can also be used as the         salts, derivatives, isomers, polymorphs, or esters thereof.     -   5. At least one Non-Steroidal Anti-inflammatory Drug (NSAID). A         preferred embodiment of the subject composition comprises         ketoprofen, preferably ketoprofen HCl as an NMDA-receptor         antagonist component of the subject composition. Ketoprofen HCl,         USP, is commercially available from Letco Medical (Decatur,         Ala.). Examples of other NSAIDs that can be used in accordance         with the subject composition include, but are not limited to:         the Salicylates—aspirin (acetylsalicylic acid), Diflunisal, or         Salsalate; the p-amino phenol derivatives—Paracetamol, or         phenacetin; the Propionic acid derivatives—ibuprofen, Naproxen,         Fenoprofen, Flurbiprofen, Oxaprozin, or Loxoprofen; the Acetic         acid derivatives—indomethacin, Sulindac, Etodolac, Ketorolac,         Diclofenac, or Nabumetone; theEnolic acid (Oxicam)         derivatives—piroxicam, Meloxicam, Tenoxicam, Droxicam,         Lornoxicam, or Isoxicam; the Fenamic acid derivatives         (Fenamates)—mefenamic acid, Meclofenamic acid, Flufenamic acid,         or Tolfenamic acid; the Selective COX-2 inhibitors         (Coxibs)—celecoxib, Parecoxib, or Firocoxib; or salts,         derivatives, isomers, polymorphs, or esters thereof.     -   6. At least one serotonin-norepinephrine reuptake inhibitor         (SNRI). A preferred embodiment of the subject composition         comprises amitriptyline, preferably amitriptyline HCl as an SNRI         component of the subject composition. Amitriptyline HCl, USP, is         commercially available from Medisca (Plattsburg, N.Y.). Examples         of other SNRIs s that can be used in accordance with the subject         composition include, but are not limited to: Venlafaxine,         Desvenlafaxine, Duloxetine, Milnacipran, Levomilnacipran,         Sibutramine, and Edivoxetine, or salts, derivatives, isomers,         polymorphs, or esters thereof.

The subject composition further includes a solvent. Preferably a polar aprotic solvent, such as Dimethyl Sulfoxide (DMSO) can be used in the composition of the subject invention. DMSO is commercially available from Medisca (Plattsburg, N.Y.). Other polar aprotic solvents in this class include dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, and HMPA.

The active components (1.-6., listed above) and solvent are formulated in a pharmaceutical compounding base, such as PENcream. PENcream is commercially available from HUMCO (Texarkana, Tex.). Pharmaceutical compounding bases are well known in the art, and other pharmaceutical compounding bases may be freely substituted for PENcream.

A topical composition prepared in accordance with the present invention may comprise other skin benefiting or carrier components, including, but not limited to conditioning agents, skin protectants, antioxidants, viscosity modifying agents, film formers, emollients, surfactants, solubilizing agents, preservatives, fragrance, chelating agents, foaming or antifoaming agents, opacifying agents, stabilizing agents, pH adjustors, absorbents, anti-caking agents, slip modifiers, various solvents, solubilizing agents, denaturants, bulking agents, emulsion stabilizing agents, suspending agents, colorants, binders, conditioning agent-emollients, surfactant emulsifying agents, biological products, cosmetic soothing aids, and/or combinations thereof.

Emollients that can be used in the subject composition include, but are not limited to, the following:

-   -   1. Triglyceride esters which include, but are not limited to,         vegetable and animal fats and oils such as palm oil, castor oil,         cocoa butter, safflower oil, cottonseed oil, corn oil, olive         oil, cod liver oil, almond oil, avocado oil, palm oil, sesame         oil, squalene, kikui oil and soybean oil;     -   2. Acetoglyceride esters, including but not limited to         acetylated monoglycerides;     -   3. Ethoxylated glycerides such as ethoxylated glyceryl         monostearate;     -   4. Alkyl esters of fatty acids having 10 to 20 carbon atoms         which include, but are not limited to, methyl, isopropyl and         butyl esters of fatty acids;     -   5. Alkenyl esters of fatty acids having 10 to 20 carbon atoms         such as oleyl myristate, oleyl stearate, and oleyl oleate;     -   6. Fatty acids having 10 to 20 carbon atoms such as pelargonic,         lauric, myristic, palmitic, stearic, isostearic, hydroxystearic,         oleic, linoleic, ricinoleic, arachidic, behenic, and erucic         acids;     -   7. Fatty alcohols having 10 to 20 carbon atoms such as lauryl,         myristyl, cetyl, hexadecyl, stearyl, isostearyl, hydroxystearyl,         oleyl, ricinoleyl, behenyl, erucyl, and 2-octyl dodecanyl         alcohols;     -   8. Lanolin and lanolin derivatives including, but not limited to         lanolin, lanolin oil, lanolin wax, lanolin alcohols, lanolin         fatty acids, isopropyl lanolate, ethoxylated cholesterol and         lanolin alcohols;     -   9. Polyhydric alcohol esters, including but not limited to,         ethylene glycol mono and di-fatty acid esters, diethylene glycol         mono-and di-fatty acid esters and polyethylene glycol (200-6000)         mono- and di-fatty acid esters;     -   10. Wax esters such as beeswax, spermaceti, myristyl myristate,         stearyl stearate;     -   11. Beeswax derivatives including but not limited to,         polyoxyethylene sorbitol beeswax;     -   12. Vegetable waxes including, but not limited to, carnauba and         candelilla waxes;     -   13. Phospholipids such as lecithin and derivatives;     -   14. Sterols including, but not limited to, cholesterol and         cholesterol fatty acid esters; and     -   15. Amides such as fatty acid amides, ethoxylated fatty acid         amides, and solid fatty acid alkanolamides.

In the manufacture of a preferred embodiment of a composition of the subject invention, a formulation includes:

-   -   Gabapentin powder—22.7 g     -   Baclofen, USP, powder—18.16 g     -   Lidocaine HCl monohydrate, USP—22.7 g     -   Clonidine HCl, USP—0.908 g     -   Ketamine HCl monohydrate, USP powder—45.4 g     -   Ketoprofen USP powder—45.4 g     -   Amitriptyline HCl, USP—9.08 g     -   DMSO (reagent grade) ACS liquid—22.7 ml, and     -   PENcream base—266.952 g.

The above components are weighed and each of the pre-weighed active ingredient powders (gabapentin, baclofen, lidocaine, clonidine, ketamine, ketoprofen, and amitriptyline) are added to a mixing vessel for a commercial mixer. About 75% of the pre-weighed PENcream compounding base (approximately 200 g), and the entire amount of the DMSO solvent, is added to the active ingredient powders in the mixing vessel. The active ingredient powders, solvent and compounding base are mixed for about 2 minutes at a mixing speed level of 9. The remaining 25% of the compounding base (approximately 67 g) is then added to provide a final mixture. The final mixture is mixed for about 7 minutes at a mixing speed level of 9 until the final mixture is substantially homogeneous, forming the final composition.

A preferred embodiment of the final composition comprises, in weight percent: gabapentin—5%; baclofen—4%; lidocaine—5%; clonidine—0.2%; ketamine—10%; ketoprofen—10%; amitriptyline—2%; DMSO—5%, and PENcream base—58.8%.

The final composition can then be placed into an appropriate container and/or packaging for shipping and storage. The packaging can include listings of ingredients and instructions for use.

A composition according to the subject invention can be topically applied. Typically, a safe and effective amount of the composition is applied to the skin for the treatment of pain caused by joint stiffness, arthritis, swelling, Inflammation or edema, muscle cramps or tremors, or for relief of discomfort from sensations such as a “burning” sensation or pain, or unspecified tingling sensations in limbs or hands or feet. A safe and effective amount is typically an amount (1-5 g) which can be spread onto and cover the specific area experiencing the pain or sensation. 

1. A topical composition for pain relief, said composition comprising: about 1-20% of at least one anti-spasmodic or GABA-agonist about 1-5% of at least one local anesthetic agent about 0.1-1.0% of at least one α₂-adrenergic agonist about 1-20% of at least one NMDA-receptor antagonist about 1-20% of at least one Non-Steroidal Anti-inflammatory Drug (NSAID) about 1-10% of at least one Serotonin-Norepinephrine Reuptake Inhibitor (SNRI), and about 1-10% of at least one solvent, and about 25-75% of at least one pharmaceutical compounding base.
 2. The topical composition of claim 1, wherein said anti-spasmodic or GABA-agonist is gabapentin or baclofen, or a combination of gabapentin and baclofen.
 3. The topical composition of claim 2, wherein said composition comprises a combination of gabapentin and baclofen, said gabapentin comprising about 5% and said baclofen comprising about 4% of said composition.
 4. The topical composition of claim 1, wherein said local anesthetic agent is lidocaine.
 5. The topical composition of claim 4, wherein said lidocaine is lidocaine HCl monohydrate and comprises about 5% of said composition.
 6. The topical composition of claim 1, wherein said α₂-adrenergic agonist is clonidine.
 7. The topical composition of claim 6, wherein said clonidine is clonidine HCl and comprises about 0.2% of said composition.
 8. The topical composition of claim 1, wherein said NMDA-receptor antagonist is ketamine.
 9. The topical composition of claim 8, wherein said ketamine is ketamine HCl monohydrate and comprises about 10% of said composition.
 10. The topical composition of claim 1, wherein said Non-Steroidal Anti-inflammatory Drug (NSAID) is ketoprofen.
 11. The topical composition of claim 10, wherein said ketoprofen comprises about 10% of said composition.
 12. The topical composition of claim 1, wherein said Serotonin-Norepinephrine Reuptake Inhibitor (SNRI) is amitriptyline.
 13. The topical composition of claim 12, wherein the amitriptyline is amitriptyline HCl and comprises about 2% of said composition.
 14. The composition of claim 1 wherein said solvent is DMSO.
 15. The composition of claim 14 wherein said DMSO comprises about 5% of said composition.
 16. The composition of claim 1, wherein said pharmaceutical compounding base is PENcream.
 17. The composition of claim 16, wherein said PENcream comprises about 58.8% of said composition.
 18. A method for relieving pain, said method comprising: Providing a topical composition of claim 1, Topically applying an effective amount of said composition to the skin at a site of pain or discomfort, and Optionally, repeating as needed.
 19. The method of claim 18, wherein said composition comprises: gabapentin—5%; baclofen—4%; lidocaine—5%; clonidine—0.2%; ketamine—10%; ketoprofen—10%; amitriptyline—2%; DMSO—5%, and PENcream base—58.8%.
 20. A method of preparing a composition of claim 1, wherein said method comprises the steps of: Pre-weighing or pre-measuring Gabapentin powder—22.7 g; Baclofen, USP, powder—18.16 g; Lidocaine HCl monohydrate, USP—22.7 g; Clonidine HCl, USP—0.908 g; Ketamine HCl monohydrate, USP powder—45.4 g; Ketoprofen USP powder—45.4 g; Amitriptyline HCl, USP—9.08 g; DMSO (reagent grade) ACS liquid—22.7 ml, and PENcream base—266.952 g; Adding to a mixing vessel the pre-weighed Gabapentin powder, Baclofen powder, Lidocaine HCl monohydrate, Clonidine HCl, Ketamine HCl monohydrate, Ketoprofen powder, and Amitriptyline HCl, with about 75% of the pre-weighed pharmaceutical compounding base and 100% of the pre-measured DMSO; Mixing for about 2 minutes to form a mixture; Adding a remaining about 25% of said compounding base to said mixture, and mixing for about 7 minutes to form a homogeneous final mixture. 